Bumper device

ABSTRACT

A bumper device, wherein the front wall part ( 5 ) and the rear wall part ( 6 ) of a bumper stay ( 4 ) disposed between a bumper reinforcement ( 2 ) and a side member ( 3 ) and connected to cach other through a plurality of ribs ( 7, 8, 9, 10 ), the inner and outer ribs ( 7, 8 ) diverge forward, a projected part ( 11 ) extending inward is provided on the inner rib ( 7 ), and the width dimension ( 11 ) of the front wall part ( 5 ) is formed larger than the width dimension ( 12 ) of the rear wall part ( 6 ), whereby the inner rib ( 7 ) of the plurality of ribs (side walls) disposed between the bumper reinforcement and the side member of a vehicle body to connect the front and rear walls of the bumper stay to each other can be prevented from being bent inward.

TECHNICAL FIELD

The present invention relates to a bumper device having an improvedbumper stay.

BACKGROUND ART

There is used a bumper device for buffering an impact energy transmittedfrom a bumper reinforcement to a vehicle body as less as possible incollision of a vehicle and restraining an adverse influence on apassenger.

The bumper devices are of a type for arranging a bumper stay between abumper reinforcement extended in a width direction of a vehicle and aside member (also referred to as side frame) on each side of a vehiclebody and absorbing an impact energy mainly by plastic deformation of thebumper reinforcement and of a type of arranging a crash box in place ofthe bumper stay and absorbing the impact energy mainly by plasticdeformation of the crash box.

A bumper device of the former type is disclosed in JP-A-2001-294106. Theexample uses a front wall in line with a rear wall of a bumperreinforcement and fixed thereto, a rear wall attached to a front endportion of a side member, and a bumper stay including at least twopieces of side walls for connecting the front wall and the rear wall.

The publicly-known bumper stay teaches forming a closed hollow portionby the front wall and the rear wall, forming an open hollow portionopened to a front side by making the front wall discontinuous, bringingthe side wall into a hollow state, or arranging the side wall with anangle of inclination relative to the rear wall.

According to the pair of side walls of the bumper stay, the side wall onan inner side disposed on a center side of the vehicle is made to belonger than the side wall on an outer side and the front wall is made tocoincide with a rear of the bumper reinforcement.

When an impact force (load) by collision of the vehicle is operated tothe bumper reinforcement of the bumper device having such a bumper stay,before plastic deformation of the bumper reinforcement, a longer one,that is, the inner side of the side wall of the bumper stay is deformedto fall to the inner side and the impact force is absorbed by aremaining one of the side wall. Therefore, first, the bumper stay iscrashed and next, the impact energy is started to be absorbed by theplastic deformation of the bumper reinforcement.

The crash of the bumper stay causes to break the side member by theimpact energy, further, support of the bumper reinforcement is lost, thebumper reinforcement is produced with unexpected plastic deformation andan efficiency of absorbing the impact energy is reduced.

Therefore, it is a problem of the invention to be solved to resolve theabove-described drawback of the prior art.

DISCLOSURE OF THE INVENTION

The invention adopts technical means for arranging inner and outer sideribs connecting front and rear wall portions by attaching an angle ofinclination to diverge the ribs to a front side (preferably, 10° through45°) and forming a projected portion projected to an inner side at aportion of coupling the inner side rib and the front wall portion inorder to resolve the above-described problem.

By adopting the technical means, when an impact force (load) is operatedto a bumper reinforcement, the projected portion of the inner side ribis displaced to the inner side and slightly to a rear side and thedisplacement displaces a remaining portion of the inner side rib to beorthogonal to the rear wall portion.

The displacement enables to receive the impact force by the inner siderib substantially uniformly with other rib and therefore, the bumperreinforcement is correctly supported by the bumper stay and the impactenergy by the plastic deformation of the bumper reinforcement can highlybe absorbed.

A width direction in a vehicle width direction of the front wall portionis larger than a width dimension of the rear wall portion and a crashrange of the bumper reinforcement can be constituted widely and thecrash load can be improved. Therefrom, an initial load of the plasticdeformation can be reduced, in other words, thin-walled andlight-weighted formation of the bumper reinforcement can be constituted.

According to the invention, there is provided a bumper apparatuscharacterized in a bumper apparatus including a bumper reinforcementextended in a width direction of a vehicle and a bumper stay fixed to aside member on a side of a vehicle body, wherein the bumper stayincludes a front wall portion fixed to the bumper reinforcement, a rearwall portion fixed to the side member on the side of the vehicle body,and a plurality of ribs for coupling the two wall portions and the innerand the outer side ribs are provided with an angle of inclinationdiverging to a front side, the inner side rib includes a projectedportion projected to an inner side and a dimension in a width directionof the front wall portion is larger than a dimension in a widthdirection of the rear wall portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a bumper device according to an example ofthe invention.

FIG. 2 is a sectional view showing a bumper stay made of a steel plate(made of steel).

FIG. 3 is a plane view showing an initial state of a bumperreinforcement and a bumper stay when an offset impact force is receivedthereby.

FIG. 4 is a plane view showing a state of progressing the state by FIG.3.

FIG. 5 is a partially enlarged sectional view showing an inner side ribof the bumper stay.

FIG. 6 is a diagram showing a relationship between a stroke and a load.

BEST MODE FOR CARRYING OUT THE INVENTION

A bumper device 1 includes a bumper reinforcement 2 extended in a widthdirection of a vehicle, and a bumper stay 4 arranged between a sidemember 3 on each side of a vehicle body and the bumper reinforcement 2.

The bumper reinforcement 2 comprises an extruded member of an aluminumbased alloy material and a sectional shape thereof may be apublicly-known sectional shape in a shape of a Chinese character of

(hollow quadrangle with one say at inside thereof),

(hollow quadrangle with two stays at inside thereof),

(hollow quadrangle with a cross at inside thereof), or □ (hollowquadrangle), further, the side member 3 may be of a publicly-known shapeformed by pressing a steel plate.

The bumper stay 4 comprises an extruded member of an aluminum basedalloy material and comprises a front wall portion 5 in line with a rearface wall of the bumper reinforcement 2 and fixed thereto, a rear wallportion 6 fixed to a front end of the side member 3, and inner and outerside ribs 7, 8 and middle ribs 9, 10 connecting the two wall portions 5,6.

A dimension 11 of the front wall portion 5 in the vehicle widthdirection is made to be larger than a dimension 12 of the rear wallportion 6 in the vehicle width direction. Making a dimension of thebumper reinforcement 2 in the vehicle width direction, that is, thecrash range 11 larger enables to increase a crash load, in other words,to constitute thin-walled and light-weighted formation of the bumperreinforcement 2.

An angle of inclination θ₁ of the inner and the outer side ribs 7, 8relative to the rear wall portion 6 is made to fall in a range of 10°through 45° and the inner and outer side ribs 7, 8 are made to divergeforwardly. The middle ribs 9, 10 are orthogonal to the rear wall portion6.

A portion of coupling the inner side rib 7 and the front wall portion 5is provided with a projected portion 11 projected to the inner side. Aprojected angle θ₂ Of the projected portion 11 is preferably made tofall in a range of 55° through 90°, more preferably, 75°. A bottomportion of the projected portion 11 is made to be formed by a circulararc face of R of 1 mm through 2 mm. Thicknesses of the ribs 7, 8, 9, 10can be made to be, for example, 2 mm through 3.8 mm.

The projected portion 11 and the inner side rib 7 are coupled by acircular arc face. The circular arc face is constituted by a circulararc face of, for example, R of 20 mm.

FIG. 2 shows a bumper stay 12 formed by pressing one sheet of a steelplate. Front wall portions 5-1, 5-2, 5-3 comprise three pieces ofseparated wall portions, rear wall portions 6-1, 6-2 comprise two piecesof separated wall portions and the ribs 7, 8, 9, 10 are provided withshapes and inclinations the same as those of the example of FIG. 1.

The portion of coupling the inner side of rib 7 and the front wallportion 5-1 is provided with the projected portion 11 projected to theinner side continuous to the circular arc face of R. The width direction1₁ of the front wall portions 5-1, 5-2, 5-3 are larger than the widthdirection 1₂ of the rear wall portions 6-1, 6-2, the angle ofinclination θ₁ of the inner and outer side ribs 7, 8 is made to fall inthe range of 10° through 45°, and the projected angle θ₂ of theprojected portion 11 is made to fall in the range of 45° through 120°,preferably, 55 through 90°.

FIG. 3 and FIG. 4 show plastic deformation of the bumper reinforcement 2and a state of displacing the inner side rib 7 of the bumper stay 4 whenan impact force F by collision is operated to the bumper reinforcement.

The impact force F is received by the wide crash range 11 and the bumperreinforcement 2 is plastically deformed in the wide range in the widthdirection of the vehicle. By inclining the inner side rib 7 to the innerside, the stroke, that means state of displacing of the bumperreinforcement 2 to the rear side can be restrained to be small, smallerthan that of the prior art in the dimension between the inner side rib 7of the left and right bumper stays 4.

The example shown in FIG. 3 and FIG. 4 is referred to as a so-to-speakoffset collision and the bumper apparatus is collided with a rigidbarrier 12 at a low speed (assumed to be 8 km/h of speed per hour).

At an initial stage of collision, the projected portion 11 of the innerside rib 7 is displaced to the inner side to restrict an onset ofbuckling of the inner side rib 7 (A direction shown in FIG. 5).

In the meantime, a buckling direction of the inner side rib 7 isrestricted to a side of the middle rib 9 (inner side of section) and asshown by FIG. 4, the inner side rib 7 is displaced in B direction shownin FIG. 5. The deformation enables to input an equally distributed loadto four pieces of the ribs 7, 8, 9, 10 and absorb the impact energy byequally distributed buckling.

A further detailed description will be given of operation of theprojected portion 11 when the offset impact force F is operated to thebumper stay 4 via the bumper reinforcement 2 in reference to FIG. 5.

Whereas a component f₂ of the impact force F operated to the middle rib9 is operated in an axis center direction of buckling the middle rib 9,a component f₁ of the impact force F operated to the inner side rib isinputted to the inner side rib 7 from a skewed direction to displace theprojected portion 11 in the arrow mark A direction. The movement of theprojected portion 11 enables to finally displace the remaining portionof the inner side rib 7 in the arrow mark B direction, form the innerside rib 7 in a shape proximate to erection, bring the middle rib 9 andthe inner side rib 7 into substantially a parallel relationship andreceive the component f₁ in an axis line direction of the inner side rib7, that is, as buckling load.

Thereby, the components f₁, f₂ . . . become substantially uniformlyoperated to the respective ribs and support wide plastic deformation ofthe bumper reinforcement 2.

The bumper stay 4 having the shape shown in FIG. 1 is constituted by anextruded member of an aluminum based alloy material of 7003S-T5. Anaverage plate thickness is constituted by 2.5 mm, however, the platethickness of the inner side rib 7 is constituted by 2.8 mm, 1 ₁ isconstituted by 200 mm, 1 ₂ is constituted by 70 mm, R is constituted by20 mm, θ₁ is constituted by 25° and θ₂ is constituted by 75°.

As a comparative example, there is fabricated a bumper stay by anextruded section of an aluminum alloy material of 7003S-T5 having anaverage plate thickness of 2.5 mm including two pieces of ribs of1₁=1₂=70 mm and orthogonal to front and rear wall portions.

The same bumper reinforcement and the same side member are used and anoffset impact force test under the same condition is carried out.

A result thereof is shown in FIG. 6. According to the example of theinvention, it has been confirmed that the stroke is reduced by 20% andthe load is increased by a multiplication factor of 1.27. Further, itcan be confirmed that the crash range of the bumper reinforcement of theexample of the invention is increased.

The impact force test is carried out also with regard to the shape shownin FIG. 1 which is not provided with the projected portion 11 under acondition the same as the above-described. As shown by FIG. 6, damage ofthe body is recognized by exceeding a body resistance and effectivenessof the projected portion has been confirmed.

1. A bumper apparatus comprising a bumper apparatus including a bumperreinforcement extended in a width direction of a vehicle and a bumperstay fixed to a side member on a side of a vehicle body, wherein thebumper stay includes a front wall portion fixed to the bumperreinforcement, a rear wall portion fixed to the side member on the sideof the vehicle body, and a plurality of ribs for coupling the two wallportions and the inner and the outer side ribs are provided with anangle of inclination diverging to a front side, the inner side ribincludes a projected portion projected to an inner side and a dimensionin a width direction of the front wall portion is larger than adimension in a width direction of the rear wall portion.
 2. The bumperapparatus according to claim 1, wherein a single one of the projectedportion is provided on a side of the bumper reinforcement of inner siderib.
 3. The bumper apparatus according to claim 2, wherein an openingangle θ₂ of the projected portion falls in a range of 45° through 120°.4. The bumper apparatus according to claim 2, wherein the bumper stay isa pressed product of one sheet of a steel plate and a hollow portionbetween the respective ribs is opened to a front side or a rear side. 5.The bumper apparatus according to claim 2, wherein the bumper staycomprises an extruded member of an aluminum based alloy material andthree pieces of closed hollow portions thereof are partitioned betweenthe front and the rear wall portions by the ribs.
 6. The bumperapparatus according to claim 5, wherein a length of the outer side ribis smaller than a length of the inner side rib.